There is a continuing search for materials having desirable fragrance properties. Such materials are used either to replace costly natural materials or to provide new fragrances of perfumed types which have not heretofore been available. Especially desirable qualities for substances having interesting fragrances such as sandalwood-type fragrances are stability and persistence, paticularly in a wide variety of perfumed articles (e.g. soaps, detergents and powders) perfumed compositions and colognes, ease of manufacture and intensity of aroma.
Furthermore, according to Guenther [E. Guenther, "The Essential Oils", Vol. V. page 173, D. Van Nostrand Co., Inc., New York (1952)], East Indian sandalwood oil "has been perhaps one of the most precious perfumery materials from antiquity down to modern times, and its popularity has shown no signs of waning." This oil is widely used in perfumery, and would be even more widely used except for its limited supply and high cost.
As is well known, a need exists for synthetic substances which can be used as sandalwood substitutes or extenders. It would be most desirable to be able to synthetically provide the major odorant compounds of the natural sandalwood oil, i.e. alpha-santalol and beta-santalol, but no commercially feasible route to these chemicals is known at this time.
It would be even more desirable to provide a synthetic compound which would have many of the desirable odor qualities of a fine East Indian sandalwood oil, yet not have the potentially labile primary allylic alcohol group present in the natural santalols. A compound which would be more resistant to acidic or oxidative decomposition as well as being base stable could be even more versatile than sandalwood oil itself.
There is no obvious explanation why only slight chemical changes should have such a dramatic effect on odor intensity other than to invoke the general unreliability of odor structure relationships. Why the addition or removal of a methyl group, the removal of a double bond or the mere moving of a methyl group would essentially destroy more than 90% of the odor intensity rather than merely cause subtle odor differences comparable to the subtle chemical differences cannot be explained by any theoretical concepts in the known art.
U.S. Pat. No. 4,052,341, issued on Oct. 4, 1977 provides a sandalwood type aroma imparting material having one of the structures:
TABLE I ______________________________________ Name Structure ______________________________________ 3-Methyl-5-(2,2,3- trimethylcyclopent-3- en-1-yl)pentan-2-ol ##STR3## 3-Methyl-5-(2,2,3- trimethylcyclopentan-1- yl)pentan-2-ol ##STR4## 5-(2,2,3-Trimethyl- cyclopent-3-en-1-yl) pentan-2-ol ##STR5## 6-(2,2,3-Trimethyl- cyclopent-3-en-1-yl) hexan-3-ol ##STR6## 4-Methyl-6-(2,2,3- trimethylcyclopent-3- en-1-yl)hexan-3-ol ##STR7## 3-Ethyl-5-(2,2,3- trimethylcyclopent- 3-en-1-yl)pentan-2-ol ##STR8## 3-Methyl-5-(2,3,3- trimethylcyclopent-3- en-1-(R)-yl)pentan-2-ol ##STR9## 3-Methyl-5-(2,2,3- trimethylcyclopent- 3-en-1-(s)-yl)penta-2-ol ##STR10## 3-Methyl-5-(2,2,3- trimethylcyclopent- 3-en-1-yl)pent-3-en-2-ol ##STR11## ______________________________________
These materials are produced according to the reaction schemes:
TABLE II __________________________________________________________________________ ##STR12## ##STR13## __________________________________________________________________________ (a)R.sub.1 = H, CH.sub.3, C.sub.2 R.sub.2 = H, CH.sub.3
East Germany Pat. No. 68,936 discloses for use in the sandalwood area a compound having the structure: ##STR14## Furthermore, Chemical Abstracts Volume 72, 125008b sets forth a genus for the East German Pat. No. 68,936 encompassing the following group of compounds: ##STR15## wherein R.dbd.CH.sub.2 OH, CHCH.sub.3 OH and R.sup.1 .dbd.H,CH.sub.3 or C.sub.2 H.sub.5.
The processes of our invention using the zinc acetate catalyst provide a highly efficient advantageous, unobvious route for a number of the aforementioned compounds and in addition provide certain novel compounds heretofore unavailable having the generic structure: ##STR16## wherein one of the lines ++++ is a carbon-carbon single bond and the other of the lines ++++ is a carbon-carbon double bond and wherein X is one of the moieties ##STR17## and these compounds have unobvious and unexpected properties insofar as their perfumery properties are concerned.
The use in zinc acetate in carrying out such reactions has heretofore been unknown and is not obvious from the teachings of the prior art. Thus, Houben-Weyl, "Methoden der organischen Chemie", volume 7/1, pages 77 et seq. and "Organic Reactions", volume 16, pages 27 to 47, 69 to 78 and 177 et seq. disclose the fact that aldehydes and ketones can be converted to .alpha.,.beta.-unsaturated ketones. Temperatures of from 5.degree. C. up to 100.degree. C. are preferred for this aldol condensation ("Organic Reactions," loc.cit., page 77). The numerous catalysts used in these methods, for example alkali and alkaline earth metal hydroxides, organic bases, alkali metal salts and alcoholates promote auto-condensation of the aldehydes and ketones and therefore cause the formation of large amounts of by-products in most cases.
Furthermore, the U.S. Pat. No. 4,005,147 discloses the production of alpha,beta-unsaturated ketones by reacting in the liquid phase an aldehyde with a ketone in the presence of a catalyst consisting essentially of zinc oxide.
It is furthermore known from U.S. Pat. No. 2,549,508 that aldehydes and ketones can be converted into unsaturated ketones of high molecular weight in the gas phase at temperatures of from 500.degree. to 1000.degree. C. in the presence of a catalyst consisting essentially of zinc oxide and from 1 to 15% by weight of zirconium oxide. In this process however only low conversions and low yields are achieved. Moreover high expenditure for equipment is required for reactions in the presence of hydrogen at the said temperatures for safety reasons. Moreover cracking processes take place at the surface of the catalyst in such reactions and these have a negative effect on the life of the catalyst.
The reaction of two identical or different aldehydes or ketones in the liquid phase at elevated temperature and in the presence of a catalyst (obtained by calcining a mixture of molybdenum oxide, magnesium oxide with or without zinc oxide or compounds of these metals) to from alpha,beta-unsaturated aldehydes or ketones is known from German Pat. No. 1,203,243.
According to the method described in the said patent good conversions and very good yields of alpha,beta-unsaturated aldehydes are obtained in the condensation of aldehydes with one another, particularly in the condensation of n-butyraldehyde or 2-ethylhexenal.
The process of German Pat. No. 1,203,243 is not so suitable for the reaction of aldehydes with ketones to form alpha,beta-unsaturated ketones, considerably lower conversions and selectivities being achieved. This is particularly noticeable when not only isobutyraldehyde (i.e., and aldehyde which does not undergo autocondensation) is reacted with a ketone by the method of the said German patent, but also aldehydes are used which readily undergo autocondensation, as for example, 3,3-dimethylacrolein and citral.
Nothing in the prior art, however, implies the process of our invention using zinc acetate catalyst whereby 2,2,3-trimethyl-3-cyclopenten-1-ylalkenyl and alkylidene secondary alkanols, alkanones, cycloalkanols and cycloalkanones may be produced in a convenient, sufficient and economical manner.